Didymellina leaf
July 6, 2015
Fungal leaf spots
Pathogen
Didymellina poecilospora.
Hosts
Iris; most severe on rhizomatous iris.
Symptoms
The first symptoms are tiny, brown spots with water-soaked borders. As disease progresses, the water-soaked areas develop into irregular spots with grayish centers and dark borders. Foliage is killed, weakening the rhizomes. Disease severity worsens after bloom.
Spread
Rain and splashing water disseminate spores to adjacent plants. The disease can easily be introduced on infected plant material.
Management
Good sanitation is important. Leaf debris should be removed in the fall to reduce inoculum, which overwinters on the dead foliage. If infected debris is left in the area in the spring, the pathogen can sporulate and reinfect developing foliage.
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